Well who would have thought it? We're losing 100,000 species a year, a billion people go hungry every day because we can't grow enough, our public parks and gardens are being scythed down thanks to the cuts, our trees are being devastated by new diseases, and what is billed as the greatest and most lavish plant show on earth carries on as if we all lived in Downton Abbey.

But gawd bless the Chelsea flower show in these straitened times. This glorious jubilee year we can still buy a conservatory for a knock-down £700,000, a sundial for £60,000, a gate for £10,000 and a gothic folly complete with real gold stars for just £60,000. This may be the best place in the world to buy a beehive (without bees) for £10,000 or a sculpture covered in 23.5 carat gold. In the parallel universe of London SW3, bird boxes cost more per square foot than just about any house north of Watford.

The Royal Horticultural Society's (RHS) lame protestations that the show is still about nature and plantsmanship go unheard. What was until quite recently a curious, understated three-day local celebration of west London privilege and an exhibition of extraordinary plantmanship skills has been handed over to a breed of modern garden pest: telly presenters on the make, C-list celebs, corporate hospitality, PR companies, international perfumiers, peddlers of cheap nostalgia, fashionistas and dodgy bankers and finance groups all hoping to pollinate their bank accounts further by letting a little of mother nature's magic rub off on them.

But rampant consumerism, raunchy ornament, celebrity culture and sheer acquistiveness and self-aggrandisment aside, what actually is the point of Chelsea now? The plants are miraculous but what it promotes is a cynical, corporate view of the natural world where gardens and money inevitably blossom together, and human wealth grows naturally.

What we, the public, get is artifice. Those plants that the professional nurserymen miraculously make bloom all at the same time have been forced to grow in the kind of tropical heat no one can afford; the pests and weeds that you never see at Chelsea all lie dead after a good dose of industrial strength poisons; and the gorgeous blooms have probably been raised in disappearing peat soil. Chelsea is nature for the 1%, as much to do with our own gardens as Christian Dior is to Primark fashion.

To be fair to the RHS, it has belatedly introduced an environment bit. It is depressingly small. WaterAid is there to show us how much of the world still drinks polluted water and Farm Africa whispers above the consumerist din how a billion people need more food. This year Groundwork, the most undersung of all Britain's environmental charities, shows how to green our cities, and University of Reading scientists are explaining how plants can help reduce temperatures, control flooding and capture pollution. A few doctors and scientists are on hand to explain how all life depends on plants and that climate change will diminish us all – but that's about it.

Chelsea needs to be radically pruned and given back to the plantsmen and women, the scientists and real gardeners who have the skills to develop sustainable growth. In the richly manured soil of London SW3 the flower show is a perfect metaphor for what is seen as progress today, a shocking display of how humankind thinks it can overcome all natural limits and achieve endless growth. But unless it faces up to the new facts of life, the new breed of pest now swarming over its body, Chelsea will surely wilt and die.